1. Field of the Invention
The present invention relates to a system for aiding in the replacement of a mold of a molding unit of a machine for manufacturing containers.
The present invention relates more specifically to a system for aiding in the replacement of a mold intended to be used for the replacement of at least one mold of a molding unit equipping a machine for manufacturing containers by the forming, by means of at least one fluid under pressure, of a preform made from a plastic material having been thermally conditioned beforehand.
A unit for molding containers comprises at least:                two mold carriers which are mounted so as to be movable between at least one open position and one closed position of the molding unit, and        a mold comprising at least two molding elements capable of being brought together in order to occupy a joined position, or of being separated in order to occupy a disjoined position, each of the said at least two molding elements of the mold being adapted to be secured in a detachable manner to one of the associated mold carriers by associated securing means, the said associated securing means being adapted to be controlled when the molding unit is in the closed position between at least one securing position and one release position.        
2. Description of the Related Art
Already familiar from the prior art are machines for manufacturing containers, in particular for manufacturing bottles, flasks, etc., which containers are obtained by the forming of a preform (or a blank), which, being made of a thermoplastic material such as PET, is thermally conditioned beforehand in an oven.
Replacement of a mold is required in particular in order to be able to proceed to the manufacture of containers having different forms and/or dimensions, or even to their replacement in the event of damage and/or wear to the molding elements.
A distinction is drawn between machines described as “linear” and machines described as “rotary”, primarily as a result of their construction and their function in the course of the manufacturing cycle.
Reference is made without limitation, for example, to document WO-2008/132090 for more details, FIG. 1 illustrating schematically a manufacturing machine of the “linear” type.
Reference is similarly made without limitation to documents FR-2.796.588 or FR-2.709.264, in which FIG. 1 respectively illustrate an installation for the manufacture of containers comprising such a “rotary” machine, of which the molding units with book-like opening are supplied by transfer means with the preforms originating from the thermal conditioning oven.
“Rotary” machines for manufacturing containers comprise a variable number of molding units, which are distributed circumferentially on a carousel that is caused to rotate.
In these machines, each molding unit comprises associated means for molding in order to undertake, by means of at least one fluid under pressure, the transformation of one or a plurality of preforms simultaneously on the basis of the number of cavities of the mold.
In a manner known per se, forming of the container from a preform is obtained notably by blowing or by stretch blow-molding utilizing pressurized air.
Reference can also be made, for example, to document FR-2.764.544 for additional details relating to the means of blowing associated with the molding unit, the said means still being referred to as a “blow nozzle”.
The machines, known as rotary machines, are equipped with molding units exhibiting specific characteristics, each molding unit comprising in particular mold carriers which are generally mounted so as to be movable about an axis of rotation (and not in translation, as in the case of “linear” machines).
The mold carriers of the molding unit are thus mounted, for example, so as to be movable about an axis of rotation with vertical orientation such that the molding unit opens towards the outside of the carousel of the machine and, because of this movement constraint, a molding unit of this type is referred to as being “in the form of a pocketbook” (or having “book-like opening” in English).
Documents FR-2.659.265 or FR-2.843.714 illustrate embodiments of a molding unit with book-like opening comprising a mold consisting of at least two molding elements (or mold halves), which, provided respectively with a molding half-cavity, are secured to two associated mold carriers in a detachable manner by securing means.
In document FR-2.659.265, the associated securing means formed by screws are adapted to be displaced between at least two positions corresponding respectively to one securing position and to one release position for the molding elements, this being performed manually by at least one operator using an appropriate tool (screwdriver, Allen key) to do so.
Document WO-96/33059 illustrates a further embodiment of a molding unit with book-like opening comprising various refinements that have been brought to such units.
It should be borne in mind, first of all, that, depending on the container to be manufactured, the molding elements in fact consist either simply of two mold halves, or, as depicted in the document, of two mold halves and a separate mold bottom, in particular when the container exhibits a mold bottom of complex form, for example petaloid, capable of presenting problems at the time of demolding.
The construction of the mold of the molding unit then differs in the sense that, by comparison with that of the aforementioned document FR-2.659.265, for example, each molding element (or mold half) is divided into two distinct parts, namely and according to the terminology of this document, on the one hand, a shell holder additionally including means of cooling and, on the other hand, a shell comprising a half-cavity for molding the container.
Shells of this kind are more easily operated by hand by an operator due to their lower weight, thus not requiring the disconnection of the fluid couplings linked to the cooling function and making it possible to optimize the choice of materials for each of the parts according to the performed function, for example the choice of aluminum for the shells.
Each of the shell holders is adapted to be secured in a detachable manner to an associated mold carrier thanks to first securing means, such as screws, while the shell is adapted to be secured in a detachable manner to the shell holder by other rapid securing means distinct from the first securing means.
The position of the rapid securing means between each shell and the associated shell holder means that they are intended to reduce the time required by an operator undertaking the replacement of a mold to release the shell in place from the shell holder at the time of its disassembly, and then to secure the other shell at the time of its assembly.
In a molding unit of this type, the replacement of a mold is undertaken by at least one operator, who, with the molding unit in the open position, proceeds manually to perform the successive disassembly of one and then the other of the shells by maneuvering the said rapid securing means by means of a tool (for example a screwdriver) in order to release them, the same operations being repeated in the opposite direction in order to carry out their securing at the time of installation of each of the other shells.
As a consequence, irrespective of the design of the mold in the molding unit and the associated securing means utilized, there is no doubt that the solutions of the prior art for undertaking the replacement of a mold all call for a succession of a large number of operations to be carried out manually by one or a plurality of operators.
In terms of disassembly, for example, a single operator or occasionally two operators intervene manually on the molding unit in order to proceed successively to opening the molding unit, to releasing the molding element (whether it is a mold half or a shell half), and to removing it by performing a circular movement of the said released molding element from the back towards the front and out of the associated mold carrier, these operations being repeated for the other molding element, to which operations are added, where appropriate, the disassembly of the mold bottom.
It is for this reason that the known solutions for undertaking the replacement of a mold in a molding unit of this kind are not considered satisfactory, in particular because of the considerable time required in order to carry out such a replacement and, in particular, the economic consequences associated with the complete standstill of the manufacturing machine.
Furthermore, in the case of molding units with book-like opening, all the operations—carried out by a single operator or occasionally by two operators for the purpose of undertaking a mold replacement—are made complicated and are slowed down by difficulties associated with access to the molding elements of the mold, since the general environment of such a molding unit with book-like opening only offers greatly reduced accessibility, the distance between the mold carriers in the open position being determined in relation to the final container to be removed from the mold in the operating mode, known as the manufacturing mode.
Furthermore, in a machine, the distance between the mold carriers in the open position is also limited by the space between the mold units, that is to say for a given molding unit, by each of the adjacent molding units situated upstream and downstream, two consecutive molding units not being able to occupy the open position simultaneously without their mold carriers coming into contact.
The length of time required to undertake the replacement of a mold must then be multiplied by the number of molding units comprising the manufacturing machine, which number of molding units with book-like opening lies, for example, between 6 and 34.
The reduction in the time necessary to replace a mold nevertheless remains a high expectation of the users of a machine for the manufacture of containers, in particular users who undertake frequent mold changes.
In fact, the machine in certain cases is not dedicated to the permanent manufacture of a single type of container, but is used to manufacture containers with different capacities and/or different forms entailing very frequent mold replacements, the attention devoted to the time or replacement of the mold of a molding unit being even greater for that reason alone and on a level with the economic challenges involved.
The immobilization of the machine during these interventions in order to replace the molds represents a major cost element because of the complete shutdown of production by which it is accompanied, and the interventions for replacing the mold are costly as a result.
Thus, the question of reducing the time for replacing the mold of a molding unit arises regardless of the design of the mold, that is to say that the two molding elements are constituted by two mold halves or are each constituted by a shell and shell holder.